This invention relates to an electrosurgical system for the treatment of tissue in the presence of an electrically-conductive fluid medium, and in particular to such a system including a fluid isolation enclosure for facilitating the immersion of tissues on, or within, a patient""s body, such that the system can be operated to vaporise, coagulate, desiccate or otherwise thermally modify such tissues.
Endoscopic electrosurgery is useful for treating tissue in cavities of the body, and is normally performed in the presence of a distension medium. When the distension medium is a liquid, this is commonly referred to as underwater electrosurgery, this term denoting electrosurgery in which living tissue is treated using an electrosurgical instrument with a treatment electrode or electrodes immersed in liquid at the operation site.
Underwater surgery is commonly performed using endoscopic techniques, in which the endoscope itself may provide a conduit (commonly referred to as a working channel) for the passage of an electrode. Alternatively, the endoscope may be specifically adapted (as in a resectoscope) to include means for mounting an electrode, or the electrode may be introduced into a body cavity via a separate access means at an angle with respect to the endoscopexe2x80x94a technique commonly referred to as triangulation. These techniques are selected according to the nature, position and access to the body cavity to be treated.
When no such natural body cavity exists, one may be created using a variety of instruments or distensible balloons. This technique is used in such procedures as endoscopic saphenous vein harvesting, endoscopic extraperitoneal hernia repair, and where other subcutaneous tunnels are created to access and perform surgical procedures. Typically, the resulting pouch or cavity is not distended with fluid, and the procedure is conducted with instruments typical of those used to perform laparoscopic surgery (endoscopic surgery performed in the abdominal cavity). Laparoscopic surgery is also performed under gaseous or mechanical distension.
Electrosurgery is usually carried out using either a monopolar instrument or a bipolar instrument. With monopolar electrosurgery, an active electrode is used in the operating region, and a conductive return plate is secured to the patient""s skin. With this arrangement, current passes from the active electrode through the patient""s tissues to the external return plate. Since the patient represents a significant portion of the circuit, input power levels have to be high (typically 150 to 250 watts), to compensate for the resistive current limiting of the patient""s tissues and, in the case of underwater electrosurgery, power losses due to the fluid medium which is rendered partially conductive by the presence of blood or other body fluids. Using high power with a monopolar arrangement is also hazardous, due to the tissue heating that occurs at the return plate, which can cause severe skin burns. There is also the risk of capacitive coupling between the instrument and patient tissues at the entry point into the body cavity.
With bipolar electrosurgery, a pair of electrodes (an active electrode and a return electrode) are used together at the tissue application site. This arrangement has advantages from the safety standpoint, due to the relative proximity of the two electrodes so that radio frequency currents are limited to the region between the electrodes. However, the depth of effect is directly related to the distance between the two electrodes; and, in applications requiring very small electrodes, the inter-electrode spacing becomes very small, thereby limiting tissue effect and output power. Spacing the electrodes further apart would often obscure vision of the application site, and would require a modification in surgical technique to ensure correct contact of both electrodes with tissue.
When either bipolar or monopolar electrosurgery is employed on the skin surface, there is a high risk of excessive thermal damage and tissue carbonisation. This is because the epidermis of the skin has a much higher electrical impedance than more vascular or moist tissues. Such thermal damage and carbonisation can lead to delayed healing, wound infection and excessive scar formation. In addition to these problems, when using bipolar arrangements, the impedance of the electrical contact between the skin and the return electrode can significantly reduce effectiveness. To overcome this problem, prior devices known in the art such as that of U.S. Pat. No. 4,202,337, use multiple arrangements of bipolar pairs in blade or needle-like electrode structures which penetrate the high impedance, superficial layers of the epidermis, such that one or more of the return electrodes makes adequate electrical contact with the tissue.
There have been a number of variations to the basic design of the bipolar probe. For example, U.S. Pat. No. 4,706,667 describes one of the fundamentals of the design, namely that the ratio of the contact areas of the return electrode and of the active electrode is greater than 7:1 and smaller than 20:1 for cutting or ablation purposes. When a bipolar instrument is used for desiccation or coagulation, for example as described in U.S. Pat. No. 5,403,311, the ratio of the contact areas of the two electrodes must be reduced to approximately 1:1 to avoid differential electrical stresses occurring at the contact between the tissue and the electrode(s).
The electrical junction between the return electrode and the tissue can be supported by wetting of the tissue by a conductive solution such as normal saline. This ensures that the surgical effect is limited to the active electrode, with the electric circuit between the two electrodes being completed by the tissue. One of the obvious limitations with such a design is that the active electrode (such as a needle) must be completely buried in the tissue to enable the return electrode to complete the circuit. Another problem is one of orientation: even a relatively small change in application angle from the ideal perpendicular contact with respect to the tissue surface, will change the contact area ratio, so that a surgical effect can occur in the tissue in contact with the return electrode.
Cavity distension provides space for gaining access to the operation site, to improve visualisation, and to allow for manipulation of instruments. In low volume body cavities, particularly where it is desirable to distend the cavity under higher pressure, liquid rather than gas is more commonly used due to better optical characteristics, and because it washes blood away from the operative site.
The applicants have found that it is possible to use a conductive liquid medium, such as normal saline, in underwater endoscopic electrosurgery in place of non-conductive, electrolyte-free solutions. Normal saline is the preferred distension medium in underwater endoscopic surgery when electrosurgery is not contemplated, or a non-electrical tissue effect such as laser treatment is being used. Although normal saline (0.9% w/v; 150 mmol/l) has an electrical conductivity somewhat greater than that of most body tissue, it has the advantage that displacement by absorption or extravasation from the operative site produces little physiological effect, and the so-called water intoxication effects of non-conductive, electrolyte-free solutions are avoided.
The applicants have developed a bipolar instrument suitable for underwater electrosurgery using a conductive liquid medium. Further details of the instrument and its operation are disclosed in the specification of our European patent application 96918768.1, the contents of which are incorporated herein by way of reference. Operation of this instrument requires that it is immersed in the electrically-conductive fluid, such that the fluid completes an electrical circuit between the two electrodes axially disposed on the shaft of the instrument. The instrument is connected to an electrosurgical generator of the type described in the specification of our European patent application 96304558.8, the contents of which are incorporated herein by way of reference, such that, in operation, the active or tissue treatment electrode of the instrument can produce vaporisation, coagulation, desiccation or thermal modification of tissue structures.
The requirement to immerse the instrument of 96918768.1 limits use to areas of the body which have natural boundaries such that a cavity is formed of dimensions and anatomical position suitable for distension with electrically-conductive liquid, for example in joints, the uterus, the bladder/urethra and the cranial cavity.
U.S. Pat. No. 4,381,007 describes the use of a rubber skirt which acts as a damming device for conductive coolant fluid used to bath the cornea of the eye. The purpose of the fluid is to support current flow between two or more electrodes arranged symmetrically and at prescribed distances from the cornea, such that the superficial surface is cooled, whilst tissues deep to the surface are treated sufficiently to correct refractive errors.
The practice of subcutaneous tunneling is also becoming common practice in order to create an artificial cavity in tissues for the purpose of performing endoscopic surgery. Typically, conventional bipolar or monopolar instruments are used, as these artificial cavities are not distended with fluid. These cavities are created between tissue planes using inflatable balloons or expandable blunt instruments through which an endoscope and instruments may be inserted.
The specification of our European patent application 97900315.9, the contents of which are incorporated herein by way of reference, describes an alternative embodiment of the instrument of 96918768.1 and an application of such an instrument to produce thermally-induced shrinkage of the pelvic floor as a corrective treatment of bladder neck descent.
The present invention provides an electrosurgical system comprising a radio frequency generator, an electrosurgical instrument, and a fluid enclosure, the generator having a radio frequency output for delivery of power to the electrosurgical instrument when immersed in an electrically-conductive fluid, the electrosurgical instrument having an electrode assembly at the distal end thereof, the electrode assembly comprising a tissue treatment electrode, and a return electrode axially spaced therefrom in such a manner as to define, in use, a conductive fluid path that completes an electrical circuit between the tissue treatment electrode and the return electrode, wherein the fluid enclosure is adapted to surround an operation site on the skin of a patient or an incision leading to a cavity surgically created within the patient""s body, wherein the fluid enclosure includes sealing means for sealing against the patient""s tissue, and wherein the fluid enclosure includes at least one port through which the electrosurgical instrument is insertable, and through which the electrically-conductive fluid can enter and/or leave the enclosure.
Advantageously, the fluid enclosure is provided with an inlet through which the electrosurgical instrument can be inserted, and preferably the fluid enclosure is provided with port means for supplying electrically-conductive fluid to, and removing said fluid from, the fluid enclosure. The fluid enclosure may be provided with a fluid inflow tube and a fluid outflow tube, each of which is associated with a respective port in the fluid enclosure. Conveniently, the fluid inflow tube is provided with a plurality of apertures at the distal end portion thereof.
Preferably, the inlet is adapted to receive an endoscope, the electrosurgical instrument being insertable, in use, through the endoscope. In this case, the fluid enclosure may be provided with a port through which electrically-conductive fluid can be removed from the enclosure, a working channel within the endoscope constituting a channel for delivering electrically-conductive fluid to the interior of the fluid enclosure.
In a preferred embodiment, the fluid enclosure is provided with a window, through which a surgeon can visualise the region surrounding the tissue treatment electrode. The window may be a magnifying window.
In one preferred arrangement, the electrosurgical instrument is a monopolar instrument having a single, tissue treatment electrode at the distal end thereof, and a metal collar positioned, in use, adjacent to the tissue treatment electrode constitutes the return electrode, the metal collar and the tissue treatment electrode being connected to the generator.
Advantageously, the fluid enclosure is such that it covers an area of skin surrounding the operation site or incision that is substantially larger than the area of the operation site or incision, whereby the volume of electrically-conductive fluid contained in the fluid enclosure is sufficiently large to ensure that its heat capacity is effective to remove heat away from tissue being treated.
In a preferred embodiment, the sealing means is constituted by an outwardly-extending flange provided on the fluid enclosure. Preferably, the flange is integrally formed with the fluid enclosure.
This fluid enclosure ensures that the electrosurgical instruments of any of the patent applications identified herein can be utilised on the surface of the body or anatomical structure to vaporise, coagulate, desiccate or thermally modify a variety of tissues.
Moreover, the fluid enclosure may be used to establish and maintain a fluidic distension of artificial cavities during use of such instruments to vaporise, coagulate, desiccate or thermally modify a variety of tissues.
In either case, the fluid enclosure may also include instrument access means to convert standard endoscopic dissection instruments, such that they can be utilised to desiccate or coagulate tissue structures utilising the generator described in the specification of our European patent application 96304558.8.
Our European patent application 96918768.1 relates to an electrosurgical instrument for producing thermally-induced shrinkage of the pelvic floor as a corrective treatment of bladder neck descent. The present invention provides access to the pelvic floor to facilitate one method of doing this.
The invention also provides a fluid enclosure device for use in -electrosurgical procedures, the device comprising a translucent flexible web member having a sealing flange at its periphery for forming a substantially fluid-tight seal with a patient""s skin thereby to enable tissue to be treated within a substantially fluid-tight enclosure provided by the patient""s skin and the flexible web member, and at least a first aperture in the web member to enable introduction of an electrosurgical instrument into the enclosure while maintaining integrity of the substantially fluid-tight seal.
Advantageously, the device further comprises a second aperture to enable supply of electrically-conductive fluid within the enclosure, a third aperture to enable removal of waste matter from within the enclosure, and a fluid outflow tube extending from the third aperture into the enclosure, the outflow tube being buoyant in electrically-conductive liquid.
The invention further provides a method of treating tissue using an electrosurgical system comprising an electrosurgical generator adapted to generate a radio frequency oscillating voltage output across first and second output terminals; an electrosurgical instrument having an active tissue treatment electrode connected to the first generator output terminal; fluid delivery means for delivering electrically-conductive fluid to the tissue to be treated; and a return electrode connected to the second generator output terminal, the method comprising the steps of: enclosing, in a substantially fluid-tight manner, a space within which the tissue to be treated is located, and within which at least the active electrode is located; operating the fluid delivery means at least partly to fill the space with electrically-conductive fluid; operating the generator to apply a radio frequency voltage between the active and return electrodes, and completing at least a part of a conduction path between the active and return electrodes using the electrically-conductive fluid; and manipulating the active electrode in the vicinity of the tissue to be treated.
Advantageously, the method further comprises the step of positioning the return electrode within the space.
Preferably, the electrosurgical instrument comprises a shaft, and the active and return electrodes are located on a distal end of the shaft, the method further comprising the steps of positioning the proximal end of the shaft to extend out of the space, and manipulating the active electrode by moving the proximal end of the shaft.
Conveniently, electrically-conductive fluid is supplied to the space continually, and the method further comprises the step of removing waste matter from within the space.
The space may be enclosed by means of a flexible enclosing member which forms a seal with a patient""s skin, and the method further comprises the step of reducing the pressure within the space to a level below air pressure in the immediate vicinity outside the space. Alternatively, the space may be enclosed by means of a flexible enclosing member which forms a seal with a patient""s skin, and the method further comprises the step of adhesively fixing the flexible member to the patient""s skin.
Preferably, the enclosing step is such that the space encloses a region of the epidermis. In this case, the active electrode may be manipulated to achieve at least one of the following: treatment of skin lesions; removal of tumours; dermabrasion; reduction of wrinkles; removal of wrinkles; treatment of solar keratosis; treatment of basal cell carcinoma.
Alternatively, the enclosing step is such that the space encloses a cavity within which the tissue to be treated is situated. The cavity may be a natural body cavity. In this case, the active electrode may be manipulated to achieve at least one of the following: thermal modification of collagen fibres, treatment of parenchyma and mesanchymal tumours. The thermal modification of collagen fibres may be performed to correct bladder neck descent or to treat ligaments or tendons.
One advantage of the invention is that immersion of tissue structures, such as skin, in the electrically-conductive fluid, reduces the impedance of the electrosurgical output, such that skin surfaces can be cut, vaporised, contoured (cutaneous thermabrasion) or otherwise thermally modified, whilst minimising char formation and undesirable thermal damage to tissue margins. This is particularly advantageous when debriding wounds or ulcers, and in the treatment of a variety of cutaneous or dermatological disorders. Such disorders include: malignant tumours (whether primarily or secondarily involving the skin); port wine stains; telangiectasia; granulomas; adenomas; haemangioma; pigmented lesions; nevi; hyperplastic, proliferative and inflammatory fibrous papules; rhinophyma; seborrhoeic keratoses; lymphocytoma; angiofibromata; warts; neurofibromas; condylomata; keloid or hypertrophic scar tissue.
Another advantage of the invention is that the desiccation capability is considerably improved by the immersion of structures in the electrically-conductive fluid, particularly as it applies to simple probe type devices such as hooks. This is a result of several factors. The first of these relates to the fact that tissue surfaces dry out quite quickly during surgical procedures, which increases the impedance of electrical contact with tissues. As desiccation performance is current-driven, the high impedance prevents adequate current delivery, and the output impedance of a desiccate voltage range is exceeded. As a result, the tissue is incompletely desiccated and, if this occurs during desiccation of a blood vessel, the lumen will still be patent and any bleeding will not be controlled. The second of these factors occurs as a result of this high impedance tissue adhering to the surface of the tissue treatment electrode. This compounds the problem, as it further reduces the effectiveness of desiccation. The third is that both these factors are enhanced when the tissue treatment electrode has a small contact surface area, particularly if this electrode is a hook which has been used for cutting, as this leads to carbonisation and pitting of the electrode surface, prior to use as a desiccating instrument. These disadvantages are overcome by use of the present invention. In particular, the improved desiccation performance is useful when sealing venous or thin-walled vascular structures as may be encountered during treatment of haemangioma, varicosities or other vascular anomalies as well as during venous harvesting.
Yet a further advantage of the present invention is that the irrigation of artificial cavities with an electrically-conductive or physiological solution, such as normal saline, provides a number of benefits. The surfaces of tissues exposed during the procedure are prevented from dehydrating, thereby improving their viability, particularly when the healing process is initiated. Tissue debris, electrosurgical smoke and blood are washed from the operative site so improving visualisation. Such devascularised debris produces tissue reactions which could potentially delay healing, increase post-operative pain associated with inflammatory mediators, and increase the risk of wound infection. The consistency of electrical performance of the invention is improved by immersion of the operative site in an electrically-conductive liquid, whereby the voltage potential required to initiate an arc in vapour is more constant compared to the variable effects of different gaseous environments on arc potential.
Still another advantage of the present invention is in providing tunnelled access to tissue structures for which, when immersed in an electrically-conductive fluid, the desiccation function can be utilised thermally to modify these structures. Such access techniques can be used to modify collagen-containing tissues which have become lax for a variety of reasons. The laxity of support ligaments is a common cause for prolapse or descent of structures which, when not supported correctly, commonly do not function correctly. An example of such a situation is bladder neck descent in women, wherein the closure mechanism of the bladder becomes ineffective under conditions of stress, such as straining, coughing or physical activity. The ligaments of the bladder neck and pelvic floor could be accessed by tunneling through the perineum to create a working cavity adjacent to these support structures. Such a cavity can then be distended by utilising the present invention for the purposes of modifying these support structures.